Use of a Broken or Risky Cryptographic Algorithm in cryptography Module
Using weak ciphers for cryptographic algorithms can pose significant security risks, and it's generally advised to avoid them in favor of stronger, more secure algorithms. Here's some guidance that advises against using weak ciphers like ARC4, IDEA, and Blowfish:
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NIST Recommendations: The National Institute of Standards and Technology (NIST) is a widely recognized authority on cryptographic standards. NIST advises against using weak ciphers in their Special Publication 800-175B: "Guide to Secure Web Services." They recommend the use of stronger ciphers like AES (Advanced Encryption Standard) and SHA-256 for cryptographic purposes.
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IETF Standards: The Internet Engineering Task Force (IETF) publishes standards and guidelines for secure network communication. IETF has deprecated or discouraged the use of weak ciphers in various RFCs (Request for Comments). For example, RFC 7465 advises against using SSLv3 and RC4 due to their vulnerabilities.
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OWASP Guidelines: The Open Web Application Security Project (OWASP) provides guidelines for secure web applications. Their guidance explicitly recommends avoiding weak ciphers, including ARC4, IDEA, and Blowfish, due to known security weaknesses.
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PCI DSS Compliance: The Payment Card Industry Data Security Standard (PCI DSS) mandates the use of strong cryptographic algorithms. Using weak ciphers is discouraged and can lead to non-compliance with PCI DSS requirements.
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Industry Best Practices: Various cybersecurity experts and organizations, such as SANS Institute, CERT/CC (Computer Emergency Response Team Coordination Center), and security vendors, provide guidance on best practices for cryptographic algorithms. These resources typically recommend avoiding the use of weak ciphers.
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Security Research: Academic papers and security research often highlight the vulnerabilities of weak ciphers like ARC4, IDEA, and Blowfish. These findings reinforce the importance of avoiding these ciphers in security-critical applications.
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Compliance Standards: Depending on your industry and location, there may be specific regulatory requirements that prohibit the use of weak ciphers. Ensure compliance with applicable regulations by using strong, approved cryptographic algorithms.
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TLS/SSL Configuration: If you are configuring web servers or other network services that use TLS/SSL for encryption, it's essential to configure your server to support only strong ciphersuites and protocols. Weak ciphers, such as RC4, have known vulnerabilities and should be disabled.
In summary, there is a consensus among reputable standards organizations, industry experts, and security professionals that weak ciphers like ARC4, IDEA, and Blowfish should be avoided due to their known vulnerabilities and weaknesses. Instead, it is advisable to use stronger, more secure cryptographic algorithms and adhere to industry best practices and regulatory requirements for encryption and security.
Example
import os
from cryptography.hazmat.primitives.ciphers import Cipher
from cryptography.hazmat.primitives.ciphers import algorithms
key = os.urandom(32)
algorithm = algorithms.ARC4(key)
cipher = Cipher(algorithm, mode=None)
encryptor = cipher.encryptor()
ct = encryptor.update(b"a secret message")
Remediation
It is advisable to use stronger, more secure cryptographic algorithms such as AES.
import os
from cryptography.hazmat.primitives.ciphers import Cipher
from cryptography.hazmat.primitives.ciphers import algorithms
from cryptography.hazmat.primitives.ciphers import modes
key = os.urandom(32)
iv = os.urandom(16)
algorithm = algorithms.AES(key)
cipher = Cipher(algorithm, mode=modes.CBC(iv))
encryptor = cipher.encryptor()
ct = encryptor.update(b"a secret message") + encryptor.finalize()
False Positives
In the case of a false positive the rule can be suppressed. Simply add a
trailing or preceding comment line with either the rule ID (PY502) or
rule category name (use_of_a_broken_or_risky_cryptographic_algorithm).
- Using rule ID
- Using category name
import os
from cryptography.hazmat.primitives.ciphers import Cipher
from cryptography.hazmat.primitives.ciphers import algorithms
key = os.urandom(32)
# suppress: PY502
algorithm = algorithms.ARC4(key)
# suppress: PY502
cipher = Cipher(algorithm, mode=None)
encryptor = cipher.encryptor()
ct = encryptor.update(b"a secret message")
import os
from cryptography.hazmat.primitives.ciphers import Cipher
from cryptography.hazmat.primitives.ciphers import algorithms
key = os.urandom(32)
# suppress: use_of_a_broken_or_risky_cryptographic_algorithm
algorithm = algorithms.ARC4(key)
# suppress: use_of_a_broken_or_risky_cryptographic_algorithm
cipher = Cipher(algorithm, mode=None)
encryptor = cipher.encryptor()
ct = encryptor.update(b"a secret message")